1. Field of the Invention
The present invention relates generally to dielectric resonators and more particularly to dielectric resonance device including one or a plurality of dielectric resonators each having a hollow frame body with an internal dielectric material disposed therein and a conductive material on the outer surfaces thereof.
2. Description of the Prior Art
In the prior art, TM-mode dielectric resonators are typically arranged to have a hollow frame body, sometimes called the "cavity" in the art, with an internally disposed dielectric material and a conductive material acting as an earth conductor disposed on the outer surfaces of the frame body. To provide easy assembly, these components are arranged in such a manner that the frame body consists of a rectangular cylindrical member having two openings at the opposite ends thereof with the dielectric material being disposed therein, and four outer surfaces (i.e., the top, bottom and two side wall surfaces) on which conductive layers are formed as the earth conductor. The inner dielectric material is comprised of a cross-coupled pillar member having two pillars, one of which extends horizontally to be coupled with two opposed inner surfaces of the side walls of frame body and the other of which extends vertically to be coupled with the other two opposed, top and bottom inner surfaces of the same.
In the manufacture of a multiple-stage dielectric resonance device including an array of dielectric resonators which are sequentially coupled to one another to provide a desired filter function, two adjacent ones of the resonators are disposed so that corresponding openings of the resonators face each other, and a conductive earth plate is attached by soldering to neighboring outer conductors on the outer surfaces of the resonators, thus causing the two adjacent resonators to be fixedly coupled to each other. Such resonator structure has been disclosed, for example, in Japanese Utility-Model Application No. 1-172702.
Unfortunately, such a conventional "conductor-soldering" resonator structure suffers from a problem in that an increased amount of heat may be generated at or in the vicinity of the soldered portions of neighboring dielectric resonators. In addition, soldering is a labor intensive and time consuming process, which causes the manufacturing process to decrease in efficiency while letting it become somewhat dangerous to factory workers.
The reasons for this will be described with reference to FIG. 8. In FIG. 8, there is illustrated in cross-section a prior art dielectric resonator structure, which employs a metal panel that is fixed to one opening of a resonator frame body in the case where two neighboring dielectric resonators are coupled together by soldering a conductive plate at its opposite ends to respective outer conductors of the resonators. As shown in FIG. 8, the frame body has a cross-coupled dielectric pillar member 4 integrally disposed in the inner space thereof. The frame body also has conductive layers 2 acting as the earth conductors which are formed on respective outer surfaces of the frame body. The frame body has a pair of openings at its opposite ends, at which openings two metal panels 8, 9 are disposed. These metal panels are coupled to the frame body using relatively thin conductive plates 6 by soldering each conductive plate 6 at its respective ends to the outer conductor 2 and to one edge of a corresponding metal panel 8 (or 9) opposed thereto. One of the metal panels, i.e., the front panel 8 in this case, has a hole for attachment of a known input/output connector 10 on it while a coupling loop 11 is used for electrically coupling the coupling loop 11 with the front panel 8. The whole structure is packed into a casing 12.
In the prior art resonator structure of FIG. 8, since the metal panels 8, 9 are designed to function also as a part of the casing 12, it is required that these panels be thick enough to provide a certain physical strength as required for the casing 12. In particular, when the input/output connector 10 is attached to and mounted on the metal panel 8, this panel 8 is required to be tough or stiff enough to fixedly hold the input/output connector 10 thereon; otherwise, when the connector 10 is twisted manually by a user, the panel 8 may possibly change shape causing the dielectric resonator to vary in its electric characteristics. To attain such stiffness, the metal panel should be thicker accordingly. However, as the panel thickness increases, the occurrence of heat diffusion becomes more severe during the soldering process at or in the vicinity of soldering portions of the resonator structure. This brings a more serious problem in that when an array of dielectric resonators are combined together into one integral form using a large-size metal panel, not only the resonators but also the metal panel must be preheated using an oven before the execution of the soldering process. This requires labor-intensive manufacturing steps at high temperatures which causes productivity to decrease. Moreover, such a process is dangerous to factory workers.